Effect of sample preparation on the accuracy of determination of composition of fluid released from quartz by gas chromatography during thermal opening of inclusions

The effect of sample preparation on the accuracy of carbon dioxide and water determination in fluid inclusions contained in quartz by pyrolytic gas chromatography is considered. It is established that careful control of quartz at all stages of sample preparation is necessary to obtain correct results. It is shown that exclusion of the stage of preliminary selection of quartz grains under a binocular microscope, even in the case of studies of high-purity, transparent quartz, can lead to significant errors in determining the content of carbon dioxide and water. It is established that in cases when quartz grains contain intergrowths with inclusions of magnetic and weakly magnetic minerals and/or are covered with iron oxide films, standard sample preparation procedures including quartz crushing, selection of a monomineral fraction, treatment with heated acid solutions, thorough washing in bidistilled water with subsequent drying, are insufficient when using pyrolysis as a method for opening inclusions. In this connection, to correlate the obtained data with the composition of fluid inclusions in such samples, it is recommended to include an additional stage in sample preparation — the electromagnetic separation.